Experimental study on post repair performance of reinforced concrete beams rehabilitated and strengthened with CFRP sheets. A thesis

摘要

Beam is a major structural load transferring Member that support the transverse load which usually rest on support at its ends. According to the revised codes, beams should have been better flexural, shear and torsion strength in addition to the load transferring capacity. It is been a major concern in construction industry in previous many years to increase the strength of the newly constructed beams or already existing beam. The recent researches have led to various innovations in high strengthening of beams due to developments, such as FRP NSMR (near surface mounted reinforcement for concrete structures). Various other materials such as Fibre Reinforced Concrete, Light Weight concrete and High Performance Concrete. The present study examines the shear performance and modes of failure of rectangular simply supported reinforced concrete (RC) beams designed with shear deficiencies. These members were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets and evaluated in the laboratory. Toward that goal, twelve RC beams were fabricated and strengthened with hybrid FRPs having different combinations of CFRP in shear. The beams were loaded with different magnitudes prior to strengthening in order to investigate the effect of initial loading on the behavior of the rehabilitated beam. Then beams were retrofitted with one layer as well two layers of CFRPs, then the load was increased until the beams reach failure. The experimental results showed that the shear strength of the beams was significantly increased by the CFRP sheet and that it is beneficial to orientate the FRP at 45° to the axis of the beam. The shear strength of FRP strengthened beams is usually calculated by adding individual components of shear resistance from the concrete, steel stirrups and FRP. The series of results indicated that there was considerable increase in shear capacity from 18% to 35% and also provided considerable horizontal restraint.